1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming method. Particularly, the present invention relates to an image forming apparatus capable of effectively suppressing the occurrence of image deletion and color muddiness and stably obtaining a high-quality image and to an image forming method using the same.
2. Description of the Related Art
Conventionally, amorphous silicon photoconductors have come into widespread use since they have high surface hardness and high durability and are easy to treat.
Meanwhile, in the amorphous silicon photoconductor, a discharge product generated during a charging process is likely to be adhered to the surface of a photosensitive layer, and the discharge product adhered to the surface of the photosensitive layer readily absorbs water. As a result, the amorphous silicon photoconductor is likely to generate image deletion.
In order to solve these problems, a method in which a heater is provided in an amorphous silicon photoconductor drum has been proposed.
That is, according to this method, water absorbed by the discharge product that is adhered to the surface of a photosensitive layer is evaporated by heat generated by the heater, thereby suppressing the occurrence of image deletion.
However, in the above-mentioned method, since the amount of discharge product adhered to the surface of the photosensitive layer continuously increases, it is difficult to stably remove water from the surface of the photosensitive layer. As a result, it is difficult to effectively suppress the occurrence of image deletion.
As another method of suppressing the occurrence of the image deletion, a method has been proposed which polishes the surface of an amorphous silicon photoconductor using titanium oxide particles that are added to a developer as an additive, thereby certainly removing a discharge product from the surface of the amorphous silicon photoconductor (for example, see Patent Document 1).
However, when the method disclosed in Patent Document 1 is used, it is possible to reliably suppress the occurrence of the image deletion. However, in this case, some of the titanium oxide particles are developed together with toner particles. Therefore, in particular, when a color image is formed, color muddiness occurs in the formed color image. As a result, it is difficult to obtain a high-quality image.
Accordingly, an image forming apparatus is needed which is capable of effectively suppressing the occurrence of the image deletion and the occurrence of color muddiness and stably obtaining a high-quality image, even when an amorphous silicon photoconductor is used as an electrophotographic photoconductor.
The inventors found that it was possible to effectively remove the discharge product adhered to the surface of the photosensitive layer and water absorbed by the discharge product and reduce the influence of the titanium oxide particles on image quality by using both the amorphous silicon photoconductor drum having the heater provided therein and the rotating member that polishes the surface of the amorphous silicon photoconductor drum using the titanium oxide particles, and setting a difference between the surface temperature of the amorphous silicon photoconductor drum and the outdoor temperature, the slide friction between the amorphous silicon photoconductor drum and the rotating member, and the average primary particle diameter of the titanium oxide particles in predetermined ranges. The present invention has been made on the basis of the findings.